Journal — The Tomato

The vault

The arguments live here. The README is the map.

Every odd choice is written down: what was tried, what broke routing, what was too slow on the bench, what got deleted to recover copper.

Continued inside · twenty dispatches from the log

Tomato is a build-log machine. If you love computers because you like how they are built, this is the entry point. Architecture and tradeoff still start with a new entry — not a silent edit.

The latest dispatch is from August: the paper is printed in Ashtown Valley, on the Bay Perimeter, and two 8-bit slices are inbound. Start there, or start at the origin and read forward.

Digital schematic of modular microcode control. — Fig. — Modular decode Each board carries a local EEPROM

Dispatches · every entry in the vault

13 Aug 2026 Front-page news in Ashtown Valley The paper is a 90s broadsheet. Ashtown Valley, the Bay Perimeter. GitHub in the same type. 07 Aug 2026 Ordered Tomato Boards on JLCPCB. Parts on DigiKey. The dual-LUT ALU left the screen. 02 Aug 2026 Designing additional boards The ALU was the hard part. The rest is 32-bit plumbing while fab runs. 31 Jul 2026 Falling back to 32b A 40-bit word doubled the explanation without doubling silicon on the bench. 31 Jul 2026 The lingering catch A throwaway FSM that becomes Tomato anyway — or build the rest of the machine. 30 Jul 2026 Redesign into 40b The bottleneck was the instruction word, not the ALU. The next day takes it back. 13 Jul 2026 Truth table latch If the next op is still ADD, pass operands. Keep the opcode latched. 13 Jul 2026 Pipelined FPGA — what if If the winds stop, then we die. Flexibility has a physics. 13 Jul 2026 Downgrade for an upgrade Do not fab one 240 mm monster. Cascade 16-bit cells. 13 Jul 2026 Demo ideas Fibonacci is too small. A self-programming FSM on a 4-bit slice. 13 Jul 2026 Architecture upgrade If LUT2 costs four chips, build the second LUT3. 27 Jun 2026 Elimination of mode multiplexers LUT3 feeds the adder. Logic rides the arithmetic path instead of racing it. 26 Jun 2026 ALU refinement NAND the generate. Spare gates as inverters. 74283 per nibble. 26 Jun 2026 Redesign with 74251 Three chips for a cell was the wrong optimization. Same logic, no contention. 19 Jun 2026 ALU segment display Thirty-two digits. One ROM. Latches so they stay bright. 16 Jun 2026 Microcode control modularization Split decode onto small boards with local EEPROMs so ribbons stay short. 15 Jun 2026 Multiplication and division Naïve shift-add is slow. A Wallace tree eats the board. Priority-encoder loop. 11 Jun 2026 Load/store pipeline Every opcode indexes a 48-bit microcode word. Two phases, or three if memory waits. 10 Jun 2026 Implementing the mul-div engine Multiply in four cycles. Divide is the trick. 74xx284/85 sequenced. Origin Welcome to Tomato 32 The first page of the vault. From simple gates to a machine with enormous ISA coverage.